Experimental study on the influence of temperature and humidity on the fracture properties of polyurethane grouting materials

Polyurethane grouting materials are widely utilized in dam restoration projects due to their advantages of early strength, rapid formation, high expansion and excellent impermeability. With the increasing complexity of the service environment, polyurethane grouting materials in practical engineering are influenced by factors such as ambient temperature, humidity, and external loads. These influences can lead to the emergence of damage cracks within and on the surface of the materials, which subsequently accelerate the propagation into macroscopic cracks, resulting in the deterioration of material properties. Consequently, this negatively impacts the effectiveness of the grouting repair. In this paper, the impact of service ambient temperature and humidity on the cracking process and fracture properties of polyurethane grouting materials were studied by three-point bending test. The findings revealed that the ambient temperature and humidity had insignificant influence on the failure morphology of polyurethane grouting materials, which consistently exhibited a flat and smooth surface. And the slight plastic deformation occurred around the pore edges in high temperature. With the increase of ambient temperature, degradation of the polyurethane matrix ensued, resulting in a decline in load-bearing capacity, fracture toughness, and fracture energy, accompanied by increased flexural strain. Notably, the brittleness of polyurethane became more pronounced at lower temperatures. The humidity environment slightly reduced the fracture toughness and fracture energy of polyurethane grouting materials.